CN103905359B

CN103905359B - A kind of 14443 interface OOK subcarriers demodulation methods and circuit

Info

Publication number: CN103905359B
Application number: CN201210566537.5A
Authority: CN
Inventors: 高慧
Original assignee: Beijing CEC Huada Electronic Design Co Ltd
Current assignee: Beijing CEC Huada Electronic Design Co Ltd
Priority date: 2012-12-25
Filing date: 2012-12-25
Publication date: 2017-11-03
Anticipated expiration: 2032-12-25
Also published as: CN103905359A

Abstract

The invention provides the OOK subcarriers demodulation method and circuit of a kind of 14443 interface PCD ends Physical Layer receiver.Sampling with high precision is carried out to subcarrier signal using ADC, mapping summation process is carried out in numeric field, directly demodulates data-signal, it is to avoid plastic and reconstructive is carried out to subcarrier in numeric field, simplifies demodulation flow, reduces circuit scale, possess antijamming capability.

Description

A kind of 14443 interface OOK subcarriers demodulation methods and circuit

Technical field：

The present invention relates to the OOK subcarrier demodulation techniques of 14443 interface PCD ends Physical Layer receivers, available for noncontact Read write line chip Type A 106Kbps receivers.

Background technology：

The processing of the 14443 interface non-contact reader chips docking collection of letters number, is divided into carrier wave demodulation and subcarrier demodulation two Individual step.Usual carrier wave demodulation is completed in analog domain, and the method for the demodulation of selection multiplier or envelope detection completes 13.56MHz Carrier signal demodulation.Subcarrier demodulation includes OOK demodulation according to communication protocol and baud rate difference and demodulated with BPSK, the present invention Suitable for the OOK modulation systems used under TypeA 106Kbps.

In order to reach certain antijamming capability, the demodulation of OOK subcarriers generally selects the scheme of integration demodulation in analog domain, The big complexity of its circuit scale is high, a large amount of consumption chip power-consumptions and area.In the case where technique line width constantly reduces, serious shadow Ring the performance and cost of chip.The scheme of OOK demodulation is carried out in numeric field, OOK subcarrier signals are quantized to numeric field by ADC Afterwards, subcarrier signal is subjected to plastic and reconstructive via algorithm process, filters out noise jamming, finally complete demodulation.

The present invention carries out sampling with high precision using ADC to subcarrier signal, carries out mapping summation process in numeric field, directly Demodulate data-signal, it is to avoid plastic and reconstructive is carried out to subcarrier in numeric field, simplify demodulation flow, reduce circuit scale, tool Standby antijamming capability.

The content of the invention：

The present invention provides a kind of circuit of the 14443 interface OOK subcarriers demodulation based on ADC, including analog to digital conversion circuit ADC, average sampler, mapping circuit, summation comparison circuit, half ETU timing circuits, wherein：Subcarrier signal is defeated after ADC Go out and give average sampler, set up reference value before frame starting, ADC output results and reference value are inputted into mapping circuit, to less than The sampled result of reference value is mapped, and remaining is not processed.Result input summation comparison circuit after mapping circuit is handled, Summation interval is timed by half ETU timing circuits, the result after mapping circuit processing is summed and compared, according to than Data-signal after the output demodulation of relatively result.

Realize that step is as follows based on a kind of method of the 14443 interface OOK subcarriers demodulation based on ADC：

(1) multiple spot averaging is carried out to ADC sampled results before frame starting, obtains a reference value R；

(2) half ETU timings are carried out after frame starting, judges whether sampled result Ai is less than a reference value R, if greater than equal to base Quasi- value R is not processed then；If less than a reference value R, then go to step (3)；

(3) sampled result Ai is based on a reference value R and carries out horizontal map, i.e., Ai is entered as R+ (R-Ai)；

(4) Ai is summed in timing is interval, half ETU timings terminate；

(5) judge whether summed result is more than preset value S0, half of ETU is interval herein if greater than then judgement demodulation result High level is exported, if less than half of ETU interval exports low level herein equal to then judgement demodulation result.

Multiple spot averaging is carried out to ADC sampled results before frame starting, a reference value R is obtained, it is necessary to be made an uproar in view of signal Sound and the influence of interference, increase the number of samples of a reference value as far as possible in the case of conditions permit.

Preset value S0 is in the case of a reference value R and the interval sampling number of timing product S1 and half of ETU are subcarrier Between summed result S2, carried out according to the amplitude range of subcarrier signal preset.

Brief description of the drawings：

Fig. 1 is 14443 interface OOK subcarriers demodulation flow chart

Fig. 2 is 14443 interface OOK subcarrier demodulation waveforms

Fig. 3 is 14443 interface OOK subcarrier demodulator circuit structures

Embodiment：

Below in conjunction with accompanying drawing, the present invention is illustrated.

Fig. 1, which is shown in the present invention, causes the process chart of erroneous judgement frame end to noise signal, according to concrete implementation Mode, comprises the following steps：

Step 201, multiple spot averaging is carried out to ADC sampled results before frame starting, obtains a reference value R, it is contemplated that signal Influenceed by noise and interference, increase the number of samples of a reference value as far as possible in the case of conditions permit.

Step 202, half ETU timings are started after frame starting.

Step 203, judge whether sampled result Ai is less than a reference value R, if less than a reference value R, then go to step 204；Such as Fruit then goes to step 205 more than or equal to a reference value R；.

Step 204, sampled result Ai is based on a reference value R and carries out horizontal map, i.e., Ai is entered as R+ (R-Ai).

Step 205, Ai is summed in timing is interval.

Step 206, half ETU timings terminate.

Step 207, judge whether summed result is more than preset value S0, if greater than then going to step 208；If less than equal to Then go to step 209.

Step 208, half of ETU interval exports high level to demodulation result herein.

Step 209, half of ETU interval exports low level to demodulation result herein.

Fig. 2 show the waveform being related in the present invention, including OOK subcarrier signals, ADC sampled signals, by mapping ADC sampled signals, and demodulation output NRZ waveforms.Processing to subcarrier signal is divided into the average sampling before frame starting Mapping summation after interval and frame is originated is interval.

In OOK subcarrier signals, subcarrier change width and interference are after mapping summation process, the half of summation Individual ETU is interval to influence very little to summed result, it can be understood as by subcarrier change width and interference in half of ETU area of summation Between diluted, therefore will not compared result produce influence, possess very strong antijamming capability.

Fig. 3 show the circuit structure of the present invention, and subcarrier signal is exported after ADC gives average sampler, is risen in frame Reference value was set up before beginning, ADC output results and reference value are inputted into mapping circuit, the sampled result less than reference value is reflected Penetrate, remaining is not processed.Result input summation comparison circuit after mapping circuit is handled, by half ETU timing circuits to summation Interval is timed, and the result after mapping circuit processing is summed and compared, the number after demodulation is exported according to comparative result It is believed that number.

It should be appreciated that the present embodiment is used for illustrative purposes only, rather than limitation of the present invention.Relevant technology neck The technical staff in domain, without departing from the spirit and scope of the present invention, can also make various conversion or change, therefore All equivalent technical schemes should also belong to scope of the invention by each claim.

Claims

1. a kind of method of the 14443 interface OOK subcarrier demodulator circuits based on ADC, it is characterised in that circuit turns including modulus Circuit ADC, average sampler, mapping circuit, summation comparison circuit, half ETU timing circuits are changed, wherein：Subcarrier signal passes through Exported after ADC and give average sampler, reference value is set up before frame starting, ADC output results and reference value are inputted into mapping circuit, Sampled result less than reference value is mapped, remaining is not processed；Result input summation ratio after mapping circuit is handled Compared with circuit, summation interval is timed by half ETU timing circuits, the result after mapping circuit processing is summed and compared Compared with according to the data-signal after comparative result output demodulation, it is characterised in that step is as follows：

(2) half ETU timings are carried out after frame starting, judges whether sampled result Ai is less than a reference value R, if greater than equal to a reference value R is not processed then；If less than a reference value R, then (3), wherein i >=1 are gone to step；

(4) Ai is summed in half ETU timings are interval, half ETU timings terminate；

(5) judge whether summed result is more than preset value S0, it is interval defeated if greater than then judgement demodulation result half ETU timings herein Go out high level, low level is exported if less than equal to then the half ETU timings herein of judgement demodulation result are interval, wherein, preset value S0 Between S1 and S2, the product of the interval sampling number of value R and half ETU timings on the basis of S1, S2 is that half of ETU timings interval is secondary Summed result under carrier case, according to the preset S0 of the amplitude range of subcarrier signal.

2. the method as described in claim 1, it is characterised in that multiple spot averaging is carried out to ADC sampled results before frame starting, obtained A reference value R is obtained, it is necessary to be influenceed in view of signal by noise and interference, increases a reference value as far as possible in the case of conditions permit Number of samples.